1. Field of the Invention
This invention relates to electrical switching apparatus. More specifically, the invention provides a circuit breaker having a trip mechanism that is actuated when a contactor terminal cover is opened.
2. Description of the Related Art
The need to ensure that current cannot flow to electrical equipment while that equipment is being serviced has long been recognized. One proposal to meet this need is described in U.S. Pat. No. 4,468,531, issued to J. H. Postlehwait et al. on Aug. 28, 1984. This patent describes a safety shield assembly for precluding access to the line and load stabs of a circuit breaker when that circuit breaker is disconnected from the stabs for servicing.
U.S. Pat. No. 5,572,396, issued to D. Robinson on Nov. 5, 1996, describes an electric service safety disconnect apparatus with over voltage and over current protection. The apparatus includes a circuit breaker having a plunger that moves between a retracted, closed position and an extended, open position. When in the open position, a lock may be passed through an aperture in the plunger, preventing the plunger from moving to a closed position.
There is a need to ensure that, any time electrical equipment is accessed for servicing, current to that electrical equipment is automatically cut off.
The present invention provides an apparatus for automatically tripping a circuit breaker upon opening the cover of electrical components mounted on either the line side or the load side of a circuit breaker. Such components include contactors, motor starters, etc.
The apparatus includes a plunger protruding from the housing of the circuit breaker, where it will be depressed by the opening of the cover of electrical equipment connected adjacent to the circuit breaker. A rod extends from the plunger to a location adjacent to the trip mechanism of the circuit breaker, where the rod engages the latch within this trip mechanism. Pushing the plunger will thereby rotate the latch of the circuit breaker, thereby releasing the carrier within the circuit breaker to move under spring bias to a position wherein the circuit breaker""s movable contact is moved away from the fixed contact, thereby opening the circuit breaker.
The present invention provides continued protection from current throughout the entire servicing of the equipment. As long as the cover to the equipment is open, the plunger will remain depressed, and the latch of the circuit breaker will remain in the trip position. Therefore, if someone were to attempt to close the circuit breaker using its operating handle, the latch would fail to hold the carrier in the closed position, so that the circuit breaker would open as soon as the operating handle was released.